Inductance system



May 19, 1931.

L. A. GEBHARD INDUCTANCE SYSTEM gnwntoc May 19, 1931. 1.. A. GEBHARD Re. 18,

INDUCTANCE SYSTEM Original Filed Dec. 22. 1928 2 Shets-Sheet 2 x WIH- 1 ii g 7'0 source 02113 A GeMa/n.

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Reiuued May 19, 1931 UNITED STATES PATENT OFFICE LOUIS A. GEBHARD, 0! WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO WIRED RADIO, INC., 01 NEW YORK, N. Y., A COR1 ORATION OF DELAWARE INDUCTANCE SYSTEM Original No. 1,753,408, dated April 8, 1930, Serial No. -327,988, filed December 22, 1928. Application for reissue filed March 14, 1931.

My invention relates to inductance systems in general and more specifically to inductance systems employed in thermionic tube transmltters.

An object of my invention is to provide an inductance system for high frequency transmitters of the type employing thermionic tubes having the anodes thereof cooled by a circulatory liquid.

Another object of my invention is to provide an inductance system wherein the high frequency output circuit includes the circulato system of the cooling fluid.

Still another object of my invention is to provide an inductance system wherein the cooling fluid circulates through the hi h freuency inductance of an electrically ba anced t ermionic tube transmitting system.

A further object of my invention is to rovide an inductance system including a uid cooled portion and an auxiliary portion adapted to be connected in circuit therewith with means for electrically coupling a load to the fluid cooled portion or to the auxiliary portion.

A still further object of my invention is to rovide an inductance system including a Enid cooled dual passage tubular member having means for defining the radio frequency otential of the electrical center thereof inclu ing a radio frequency path to ground through a condenser.

A better understanding of the inductance system of my invention can be had by referring to the specification following and to the accompanying drawings wherein:

Figure 1 is a diagrammatic illustration showm the inductance system of my invention an Fig. 2 is a schematic circuit diagram showing the inductance system of my invention.

In transmitting systems employing thermionic tubes having their anodes cooled by a circulatory liquid it is essential to efliciency that the losses of high frequency energy in the cooling system be reduced to a minimum. With the connection of the cooling fluid to and from the thermionic tubes by means of an insulated length of tubing or hose, considerable loss of energy occurs. This is due Serial No. 522,709.

primarily to the high potential of high frequency energy concentrated at the points of connection. The inductance system of my invention reduces these losses to a minimum and in addition provides many advantages, as will appear from the specification follow- Tig. 1 of the accompanying drawings is a diagrammatic illustration showing the inductance system of my invention. Thermionic tubes 1 and 2 are of the type adapted to have the anodes thereof cooled by a circulatory liquid. Tubes 1 and 2 are contained in receptacles or sockets 3 and 4 respectively. The cooling liquid is associated with thermionic tubes 1 and 2 by means of helical coil 5. Coil 5 comprises a length of metal havin dual passage for conveying the cooling fiui to and from the respective tubes. Coil 5 is herein illustrated as comprising individual lengths of metal tubing which are placed parallel to each other and positioned in this manner by welding or other suitable means. This provides a single electrical conductor and a dual passage for the circulating liquid. The circulating liquid is associated with coil 5 by means of connectors 5 and 5 which conduct the liquid to and from the source of supply. Coil 5 is so designed that the frequency char-' acteristics of the inductance thereof combined with the capacity of condenser 8 provides approximately the lowest frequency at which it is desired to operate the transmitter. The high frequency energy may be transferred to another circuit b inductance 13 which may be positioned in inductive relation to said coil 5 and electrically associated with the load circuit 14. Load circuit 14 may com rise a space radio radiating system, a wire radio s stem or additional thermionic tube ampli er circuits. Other coupling arrangements may be employed such as causing contact members 13'13 to be COIiIlGCtBd either directly or capacitively to coi 5.

When it is desired to operate the transmitter on a frequency higher than that obtained by employin coil 5 and capacity 8 alone, an auxiliary inductance 11 is connected in parallel with coil 5 and capacity 8. This is acwas 10 and C was 5. Assuming that the frequency characteristics of inductance 11 were such as when employed with a capacity having a'value of 5 would likewise give an oscillation constant of 50. If then inductance 11 is connected in parallel relation with coil 5 the resultant value of L would be 5 and the oscillation constant 25. A decrease in the oscillation constant is in effect an increase in the fre uency characteristics of the circuit, as is well own in the art. It is further obvious that any frequency characteristics may be had by employing the well known elementary law for parallel inductances which formula is identical with that employed for parallel connection of resistances.

Fig. 2 is a schematic circuit diagram showing the inductance system ofmy invention employed in a representative amplifier circuit arrangement. Like reference characters are employed in this illustration. The anode circuits of thermionic tubes 1 and 2 are energized from source 16.. Capacity 28 is connected to the mid-connection of coil 5 and to ground 12.

The connection of the condenser 28 to ound 12 provides a low impedance path or radio fre uency currents and serves to establish a no al point on the coil at the point,

- where the liquid is introduced and discharged.

In this way a low voltage condition exists at the oint of admission and discharge of the n1 fixed. The radio frequency potential at the electrical center of the coil is a minimum and admission or discharge of the cooling fluid may be effected with minimum losses. Inductance 11 is associated with space radio radiating system 1212 by coil 12. Coil 13 is provided by which connections to a suitable load circuit may be had when different adjustments of frequency are not properly related to the frequency characteristics of circuit 12, 12, 12 Coil 13 is inductively coupled with the fluid cooled inductance 5 and connected to any suitable load circuit such as I a wired radio circuit or an antenna ground circuit connected to the loads 14. If however the auxiliary inductance 11 is connected through switches 9 and 10 and tuned by means of condenser 8 across the fluid cooled inductance 5, the radio frequency coupling may be established through coupling coil 12 to the antenna ground system 12-12 in which event the coupling coil 13 would be disconnected and not used. The cathode circuits of thermionic tubes 1 and 2 are energized from and the electrical center of the coil is the input circuits and inductances 59 and capacity 8 constituting the output circuits. The circuits are electrically balanced by balancing condensers 20 and 21 whichprovide means for counterbalancing or neutralizing unlike characteristics of the circuits. The input circuit of thermionic tubes 1 and 2 are associated with any suitable source of high frequenc energy 19 by means of condensers 25 an 26. Capacity 24 is provided to ofler a by-path to the high frequency energy and exclude the same from source 17. Different adjustments in the frequency characteristics are obtained by opening or closing switch members 9 and 10.

Coil 5 comprises any suitable metal tubing and the inherent frequency characteristics of the inductance which it constitutes are not easily adjusted. Since the opposite ends of the coil are connected to the sockets of the. therminoic tubes and a circulatory cooling liquid is flowing therethrough, it is obvious that it would be impractical to attempt to vary the length of the tubing. In the inductance system of my invention the frequency characteristics of the circuit including coil 5 may be easily adjusted to any desired value without disturbing the circulation of the cooling fluid.

I realize that manymodifications of the inductance system of my invention are possible without departing from the spirit of my invention. Any suitable type of thermionic tubes may be employed and any number of such tubes may be connected in suitable circuit arrangements. Similar inductances may be emplo ed in the input circuit when a liquid coole inductance is necessary or so desired. It is to be understood that my invention shall not be restricted to precisely the arrangements shown in the accompanying drawings or described in the foregoing s ecification but only as defined by the scope o the appended claims. v

What I claim as new and desire to secure by Letters Patent of the United States is as 1 nected with said metallic member intermediate the ends thereof for defining the elec trical center therein and means provided at the electrical center of the inductance whereby said liquid may be admitted to said passa e.

2. n inductance system comprising a helix, said helix comprising a double passage for cooling fluid and a common passage for electrical energy, a cooling fluid inlet and discharge connection along said helix and means including a radio frequency path to ground from a point along said helix for establishing the electrical center of said' helix at said fluid inlet and discharge connections.

3. An inductance system comprising a helix, said helix comprising a dual passage conductor for cooling fluid, a common passa e for electrical energy, means for establis ing a high frequency voltage node at the electrical center of said helix for reducing the hi h frequency voltage to a minimum at said efectrical center of said helix including a radio frequency path to ground and a connecting member provided at the electrical center of said helix for admitting and discharging cooling fluid.

4. In an inductance system the combination of a helix, said helix comprising metal tubing having a double passage for the circulation of a cooling fluid means provided at the electrical center of said helix for admitting said fluid to said assages and a path to ground through a con enser connected to the electrical center of said helix for maintaining the radio frequency otential at the point nected to said lengths of metal tubing intermediate the ends thereof for fixing the electrical center of said tubing and maintaining the radio frequency potential at the point of admission and discharge of the liquid to the conductors at a minimum.

6. An inductance coil comprisin a helical formation of metallic tubing rovi ing a plurality of individual fluid cond ucting passages immediately adjacent to each other and constituting a single electrical conductor, fluid inlet and discharge connections for said tub-- ing intermediate the ends of said coil, an electrical circuit connected between said fluid inlet and discharge connections and the ground, said circuit including a lowimpedance path to radio frequency currents and operating to maintain the electrical center of said metallic tubing at minimum radio frequency potential.

7. An inductance coil comprising a helical formation of metallic tubing having a plurality of individual fluid conducting passages and a single electrical passage; a path to ground extending between the metallic tubmg at a point intermediate the ends thereof with said tubing at the electrical center of the inductance, and an electrical circuit connected to said tubing at a point intermediate the ends thereof, said circuit including a radio frequency path to ground for maintaining said tubing at a low radio frequency potential at the point of connection of said circuit thereto and defining the electrical center thereof.

9. An inductance system comprising in combination a metallic member of helical form providing a double passage for the circulation of coolin fluid, a load circuit, means for inductive y coupling said load circuit with said helical metallic member, means for defining the potential of the electrical center of said inductance including a radio frequency path to ground, and means for admitting and discharging cooling fluid at the electrical center of said inductance.

10. An inductance system comprising a metallic member of helical form providing a double passage for the circulation of coollng fluid, a load circuit, an inductance coil ada ted to be electrically connected in arafiel with said metallic member, means or conjointly tuning said metallic member and said inductance, a radio frequency path to ground connected to said metallic member intermediate the ends thereof for establishing the electrical center of said metallic member, fluid inlet and discharge connections for said metallic member at said electrical center, and independent means inductively coupled to said metallic member and to said inductance for symmetrically transferrin energy from said metallic member to said oad circuit.

11. A high frequency inductance system comprisin in combination a metallic member of helical form providing a double assage for the circulation of cooling fluid, a load circuit, an inductance conductively connected withsaid metallic member of helical form, means for conjointly tuning said inductance and said member, separate means inductively coupled to said member'and to said inductance and adapted to be electrically connected with said load circuit, means including a radio frequenc path to ground for maintalning the electrical center of said metallic member at minimum radio frequency Eotential and means. for introducing cooling uid at the minimum radio frequency potential point along said metallic member. 12. A high frequency inductance system comprising in combination a metallic member of helical form providing a double passage for the circulation of cooling fluid, a load circuit, an inductance conductlvely connected with saidvmetallic member, means for con- 10 'ointly tuning saicl inductance and said mem-' er, separate means inductivel coupled to said member and to said in uctance and adapted to be electricall connected with said load circuit, a low im ance radio frequency 15 path to ground connected to the electrical center of said metallic member for maintaining the electrical center of said metallic memher at minimum radio frequent: potential and means for introducing and ischarging 20 cooling fluid from said metallic member at said position of minimum radio frequency potential along the electrical center thereof.

LOUIS A. GEBHARD. 

